I'm a bit concerned with how specific this turbo setup is since you almost never want to be part of the first of anything of this nature, typically when that's the case you have to start factoring in the possibility of it going wrong somewhere until it has proven itself.
That's definitely a big concern. But that being said, anything new or "different" from the norm is subject to failure or flaw. If you're worried, I would wait a year or so before biting the bullet and pulling the trigger on getting one. See how the waves flow and go from there kind of thing.
This provides a good opportunity to enjoy the Boxster/Cayman with the bigger 3.8. Sadly you might like it enough to not even think about the 718, some people just won't pull themselves away from that for what the 718 offers.